The call came about 3:30 p.m. on Tuesday as a limousine carrying Myeshia Johnson and her two children, ages two and six, sat at Miami International Airport waiting for the transport plane carrying the body of her husband, Army Sergeant La David T. Johnson, to arrive.

As President Trump spoke for three to five minutes, Ms. Johnson, 24, who is six months pregnant, wept openly, her body frozen with emotion, according to Representative Frederica S. Wilson, Democrat of Florida who accompanied the young widow.

“Myeshia, the entire time, was in a ball, rolled up almost like in a fetal position crying,” Ms. Wilson said on Wednesday. “What he said was, ‘I guess he knew what he was signing up for but it still hurts.’ That’s how he said it.”

Ms. Wilson offered a harsh critique of the president’s words about the soldier’s death in an ambush in Niger, which she said were not comforting.

“So in other words, when you sign up when you go into the military, you are really signing up to die,” she said of the president’s comments. “That is not what you say to a grieving widow, a woman who just learned that her husband cannot have an open casket funeral. In fact, she will probably not even be able to see his body.”

Ms. Wilson said she became “livid” at Mr. Trump’s comments, and motioned to the military officials in the limousine that she wanted to speak with the president herself. But she said they would not allow it.

Instead, the conversation continued for several more minutes with Ms. Wilson crying.

“When she got off the phone, she said, ‘He didn’t even know his name. He kept calling him, ‘Your guy,’ ” Ms. Wilson recalled the widow saying. “He was calling the fallen soldier, ‘your guy.’ And he never said his name because he did not know his name. So he kept saying, ‘Your guy. Your guy. Your guy.’ And that was devastating to her.”

At the White House on Wednesday, Sarah Huckabee Sanders, Mr. Trump’s press secretary, defended the president’s comments. “Just because the president said ‘your guy,’ I don’t think that means he doesn’t know his name,” Ms. Sanders said.

Ms. Sanders quoted Mr. Trump as saying that, as president, “the hardest job he has is making calls like that,” and she criticized the Florida congresswoman for “the way that she’s politicized this issue, and the way that she is trying to make this about something that it isn’t.”

Long before she became a political figure, Ms. Wilson was well known in South Florida for her work with local communities — and for often donning decorative hats. Before joining the House in 2011, Ms. Wilson was a school principal, school board member, state legislator — and also has an elementary school named for her in Miami Gardens, Sergeant Johnson’s hometown.

The congresswoman said she has known Sergeant Johnson and his family for years, beginning when, in elementary school, he joined a mentoring program started by Ms. Wilson.

Sergeant Johnson was close to his family, Ms. Wilson said, and was in constant contact with his mother, calling her every day at about 7 a.m. “He calls her at the same time every morning, even from Africa, to tell her he loves her,” Ms. Wilson said.

The Pentagon has launched an investigation into the ambush in Niger that resulted in the deaths of four soldiers. Ms. Wilson said she also is demanding more information about Sergeant Johnson’s death.

A version of this article appears in print on , on Page A20 of the New York edition with the headline: Describing Phone Call At Center Of a Storm. Order Reprints | Today’s Paper | Subscribe